Primer for improving the bonding of adhesives to nonporous substrates

Abstract

A primer for promoting adhesion between an elastomeric adhesive and a nonporous substrate containing a silane-modified saturated polyester polymer and an adhesion promoter in an anhydrous solvent. The invention is also directed to a silane-modified saturated polyester polymer, and an adhesion promoter made by the reaction of a multifunctional isocyanate and an organosilane.

We claim: 
     
       1. A primer comprising: a) from about 4 to about 20 weight percent of a silane-modified polyester polymer;   b) from about 2 to about 14 weight percent of an adhesion promoter; and   c) from about 50 to about 90 weight percent of an anhydrous solvent.   
     
     
       2. The primer of claim 1 wherein the silane-modified polyester polymer has the formula: ##STR9## wherein: the ##STR10##  represents a moiety of a difunctional polyester polyol of general formula ##STR11##  X represents an ##STR12##  group or an S, and each X may be the same or different; each R represents a divalent organic moiety; each R 1  represents hydrogen or a C 1-4  alkyl group;   each R 2  represents a C 1-6  alkyl group;   each R 3  represents H, a C 1-6  organic moiety, or a second RSiR 1   n  (OR 2 ) 3-n  group, which may be the same as or different from the first such group;   each R 4  represents a divalent organic moiety; =p1 and n is 0 or 1.   
     
     
       3. The primer of claim 1 wherein the adhesion promoter is the reaction product of a multifunctional isocyanate and at least one organosilane containing an NCO-reacting hydrogen of the formula: ##STR13## or of the formula:   HSRSiR.sup.1.sub.n (OR.sup.2).sub.3-n                      (IV)     or mixtures thereof,   wherein: each R represents a divalent organic moiety;   each R 1  represents hydrogen or a C 1-4  alkyl group;   each R 2  represents a C 1-6  alkyl group;   each R 3  represents H, a C 1-6  organic moiety, or a second RSiR 1   n  (OR 2 ) 3-n  group, which may be the same as or different from the first such group; and   n is 0 or 1,     and wherein the equivalent ratio between the NCO groups of the multifunctional isocyanate and the NCO-reacting hydrogens is at least about 3.   
     
     
       4. The primer of claim 1 further comprising one or more additives selected from the group consisting of catalysts, moisture scavengers, NCO stabilizers, carbon black, non-black fillers, and defoaming agents. 
     
     
       5. A method for promoting the adhesion of an elastomeric adhesive to at least one nonporous substrate comprising treating the nonporous substrate with the primer of claim 1. 
     
     
       6. The method of claim 5 wherein the elastomeric adhesive is adhered to two different substrates, and the same primer is applied to both substrates. 
     
     
       7. The method of claim 6 wherein the elastomeric adhesive is selected from the group consisting of urethanes, silylated urethanes, silyl-terminated polyethers and silicones. 
     
     
       8. The primer of claim 3 wherein said organosilane is an amino-alkoxysilane in accordance with Formula III. 
     
     
       9. The primer of claim 3 wherein said organosilane is an amino-alkoxysilane in which R 3  is a C 1-6  organic moiety. 
     
     
       10. The primer of claim 9 wherein R 3  is phenyl. 
     
     
       11. The primer of claim 10 wherein said amino-alkoxysilane is N-phenyl-gamma-aminopropyltrimethoxysilane. 
     
     
       12. The primer of claim 3 wherein said organosilane is a mercapto-alkoxysilane in accordance with Formula IV. 
     
     
       13. The primer of claim 12 wherein said mercapto-alkoxysilane is gamma-mercaptopropyltrimethoxysilane or gamma-mercaptopropylmethyldimethoxysilane. 
     
     
       14. The primer of claim 1 wherein said silane-modified polyester polymer is the reaction product of: a) the reaction product of a difunctional polyester polyol dissolved in an anhydrous solvent with at least one difunctional isocyanate of the formula OCN--R 4  --NCO; and   b) at least one organosilane containing an NCO-reacting hydrogen of the formula: ##STR14##  or of formula:   HSRSiR.sup.1.sub.n (OR.sup.2).sub.3-n                      (IV)        or mixtures thereof,   wherein: each R represents a divalent organic moiety;   each R 1  represents hydrogen or a C 1-4  alkyl group;   each R 2  represents a C 1-6  alkyl group;   each R 3  represents H, a C 1-6  organic moiety, or a second RSiR 1   n  (OR 2 ) 3-n  group, which may be the same as or different from the first such group;   each R 4  represents a divalent organic moiety; and   n is 0 or 1.     
     
     
       15. The primer of claim 14 wherein the molar ratio of difunctional isocyanate to difunctional polyester polyol is about two to one. 
     
     
       16. The primer of claim 14 wherein the molar ratio of organosilane to the reaction product of a) is at least about two to one.